JP2003343322A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent damage caused by the generation of temperature deflection in a catalytic converter and a thin wall ceramic support in particular. <P>SOLUTION: In performing fuel cutting while an internal combustion engine is running at a reduced speed, when the accumulated displacement or the accumulated period from the start of fuel cutting exceeds a specified threshold value under the condition that the temperature of a catalysis when fuel cutting is started is higher than a specified temperature, fuel cutting is prohibited. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for preventing catalyst damage in an internal combustion engine having a catalytic converter in an exhaust passage.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Patent Laid-Open No. 10-19
There is one described in Japanese Patent No. 6433. This prohibits fuel cut when the temperature of the catalyst exceeds a predetermined temperature in order to prevent early deterioration of the catalyst. That is, the fuel cut is performed during deceleration operation in which fuel supply is unnecessary or during engine overspeed, but fuel cut induces a lean atmosphere of excess oxygen in the exhaust system, and the catalyst temperature is high. If the fuel cut is executed in, the atmosphere around the catalyst becomes a high temperature lean atmosphere and the catalyst deteriorates early. Therefore, when the catalyst temperature exceeds a predetermined temperature, the fuel cut is prohibited to prevent the catalyst from being exposed to the oxygen excess state at a high temperature to prevent the deterioration of the catalyst.

[0003]

However, if the deceleration fuel cut is uniformly prohibited when the temperature of the catalyst is high, the chances of fuel cut are reduced and the fuel consumption is deteriorated. In view of the above, the present invention prevents the catalyst from being damaged by the deceleration fuel cut, but enables the deceleration fuel cut as much as possible within the range in which the catalyst is not damaged to improve the fuel economy of an internal combustion engine. An object is to provide a control device.

[0004]

Therefore, in the present invention,
Under the condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature, the deceleration fuel cut is prohibited when the cumulative displacement or the cumulative period from the start of the deceleration fuel cut exceeds a predetermined threshold. Constitute.

[0005]

According to the present invention, even under the condition that the catalyst temperature at the start of deceleration fuel cut is high, the deceleration fuel is maintained until the cumulative displacement or the cumulative period from the start of the deceleration fuel cut exceeds a predetermined threshold value. Since it cuts, fuel consumption can be improved.
On the other hand, when the predetermined threshold is exceeded, the deceleration fuel cut is prohibited, so that the catalyst can be surely prevented from being damaged.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of an automobile engine showing an embodiment of the present invention. Air is sucked into a combustion chamber of each cylinder of an engine 1 mounted on a vehicle from an air cleaner 2 through an intake duct 3, a throttle valve 4, and an intake manifold 5. At each branch portion of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder.

The fuel injection valve 6 is an electromagnetic fuel injection valve (injector) which is energized by a solenoid to open the valve, and deenergized to close the valve, and is supplied from an engine control unit (hereinafter referred to as ECU) 12 which will be described later. The valve is energized by a drive pulse signal to open the valve, and the fuel is pressure-fed from a fuel pump (not shown) and injected and supplied with fuel adjusted to a predetermined pressure by a pressure regulator. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal.

A spark plug 7 is provided in each combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture. Exhaust gas from each combustion chamber of the engine 1 is exhausted via an exhaust manifold 8. Further, an EGR passage 9 is led out from the exhaust manifold 8, whereby a part of the exhaust gas is recirculated to the intake manifold 5 via the EGR valve 10.

On the other hand, in the exhaust passage, the exhaust manifold 8
Located immediately below the exhaust gas, and the catalytic converter 11 for purifying exhaust gas
Is provided. This catalytic converter 11 is formed by supporting a catalyst on a ceramic carrier having a honeycomb structure, and particularly as a ceramic carrier, a thin wall carrier, that is, a honeycomb partition wall having a wall thickness of 3 mils (= 3 × 25.4 / 1000).
= 0.076 mm) or less, more specifically about 2 mils (= 2 × 25.4 / 1000 = 0.051 mm).

The ECU 12 includes a CPU, ROM, RAM,
A microcomputer including an A / D converter, an input / output interface, and the like is provided, and receives input signals from various sensors and performs arithmetic processing as described below to control the operation of the fuel injection valve 6. As the various sensors, a crank angle sensor 13 capable of detecting a crank angle as well as an engine speed Ne from rotation of a crank shaft or a cam shaft of the engine 1, an air flow meter 14 detecting an intake air amount Qa in the intake duct 3, and a throttle valve. Throttle sensor 15 (including an idle switch that is turned on when the throttle valve 4 is at the fully closed position), engine 1
A water temperature sensor 16 for detecting the cooling water temperature Tw, an air-fuel ratio sensor 17 for outputting a signal according to the rich / lean of the exhaust air-fuel ratio at the collecting portion of the exhaust manifold 8, and a temperature (catalyst temperature) Tc of the catalytic converter 11 A catalyst temperature sensor 18, a vehicle speed sensor 19 for detecting the vehicle speed VSP, and the like are provided.

Here, the ECU 12 inputs the signals from the various sensors and, based on the intake air amount Qa and the engine speed Ne, the basic fuel injection amount Tp = K.Q.
a / Ne (K is a constant) is calculated, and various corrections are applied to this to obtain the final fuel injection amount Ti = Tp · COEF · α (CO
EF defines various correction coefficients, and α defines an air-fuel ratio feedback correction coefficient). Then, a drive pulse signal having a pulse width corresponding to Ti is output to the fuel injection valve 6 at a predetermined timing for each cylinder in synchronization with the engine rotation to perform fuel injection.

On the other hand, as will be described later, the ECU 12 determines whether or not there is a rotation limiter, a vehicle speed limiter, or a fuel cut condition at the time of deceleration operation, and accordingly, a fuel cut command (rotation limiter flag = 1, vehicle speed limiter Flag =
1 or the deceleration F / C flag = 1), the output of the drive pulse signal to the fuel injection valve 6 is stopped and the fuel cut is performed according to the flowchart of FIG.

That is, in the fuel injection control routine of FIG. 2, it is determined in S1 whether or not the rotation limiter flag = 1, it is determined in S2 whether or not the vehicle speed limiter flag = 1, and in S3, the deceleration F is performed. It is determined whether the / C flag = 1. As a result, if all the flags are 0, the routine proceeds to S4 to perform normal fuel injection, but if any of the flags is 1, the routine proceeds to S5 to perform the fuel cut.

FIG. 3 is a flow chart of the rotation limiter control routine, in which the rotation limiter flag is set. This routine is executed every predetermined time. Here, the rotation limiter control is executed to prevent the engine from over rotating in order to protect the engine. In S11, it is determined whether or not the rotation limiter flag = 1 indicating that the fuel is being cut by the rotation limiter. If the rotation limiter flag = 0, the process proceeds to S12.

In S12, the engine speed Ne is detected, and it is determined whether or not the predetermined permissible speed Ne1 has been exceeded. If not, the present routine is terminated. When the engine speed Ne exceeds the allowable speed Ne1, the process proceeds from S12 to S13, and the rotation limiter flag =
The routine ends as 1. As a result, fuel cut by the rotation limiter is started.

After the rotation limiter flag = 1, the process proceeds from S11 to S14 from the next time onward. In S14, the engine speed Ne is detected, and a predetermined allowable speed Ne2 is detected.
It is determined whether or not (setting is slightly lower than Ne1), and if not, the present routine is ended as it is. Thereby, the state of the rotation limiter flag = 1 is maintained and the fuel cut is continued.

If the engine speed Ne is lower than the allowable engine speed Ne2, the process proceeds from S14 to S15. In S15, the rotation limiter flag is set to 0, and this routine ends. As a result, the fuel cut by the rotation limiter is completed, and the fuel injection is restarted. FIG. 4 is a flowchart of the vehicle speed limiter control routine, in which the rotation limiter flag is set. This routine is executed every predetermined time.
Here, the vehicle speed limiter control is executed to prevent a high vehicle speed.

In S21, it is determined whether or not the vehicle speed limiter flag = 1 indicating that the fuel is being cut by the vehicle speed limiter. If the vehicle speed limiter flag = 0, the process proceeds to S22. S22
Then, the vehicle speed VSP is detected and the predetermined allowable vehicle speed VS is detected.
It is determined whether or not P1 is exceeded, and if it is not exceeded, this routine is finished as it is. Vehicle speed VSP is allowable vehicle speed VS
If P1 is exceeded, the process proceeds from S22 to S23, sets the vehicle speed limiter flag = 1, and ends this routine. As a result, fuel cut by the vehicle speed limiter is started.

After the vehicle speed limiter flag becomes 1, the process proceeds from S21 to S24 from the next time onward. In S24, the vehicle speed V
SP is detected, and a predetermined allowable vehicle speed VSP2 (VSP
(Setting slightly lower than 1) is determined, and if not, the present routine is ended. As a result, the vehicle speed limiter flag = 1 is maintained and the fuel cut is continued.

If the vehicle speed VSP is lower than the allowable vehicle speed VSP2, the process proceeds from S24 to S25. In S25, the vehicle speed limiter flag is set to 0, and this routine is finished. As a result, the fuel cut by the vehicle speed limiter is completed, and the fuel injection is restarted. 5 or 6 is a flowchart of the deceleration fuel cut control, in which the deceleration F / C flag is set.

Prior to the explanation of this flow, the problems will be organized. The catalyst damage that is a problem in the present invention includes not only deterioration due to high temperature of the catalyst portion but also temperature difference (uneven temperature) generated inside the catalyst (heat shock). For example, when the rotation limiter or the vehicle speed limiter is operating, fuel injection and fuel cut are alternately repeated, and a rich-lean atmosphere is momentarily sent to the catalyst, so that the catalyst temperature greatly rises.

If fuel cut is performed during deceleration operation when the catalyst temperature is extremely high, such as after the operation of such a rotation limiter or vehicle speed limiter or after high load operation, unburned air is sent. , The catalyst is cooled rapidly. At this time, the flow of exhaust gas becomes uneven due to the shape of the exhaust system, and the part with a large air flow such as the catalyst center part is rapidly cooled.Therefore, the temperature deviation occurs between the catalyst center part and the catalyst peripheral part. May result in damage to the catalyst.

Particularly in recent years, a ceramic carrier is used as a catalyst carrier, and a thin-walled carrier is used because it enables early activation by reducing heat mass, and this thin-walled carrier has a low strength and is therefore subject to uneven temperature. Durability is low. FIG. 7 shows changes in the catalyst temperature when shifting to the deceleration operation after the normal operation, and shows that the temperature difference between the catalyst central portion and the catalyst peripheral portion does not become so large even if the deceleration fuel cut is performed. There is.

FIG. 8 shows changes in the catalyst temperature when the high temperature state is changed to the deceleration operation. When the deceleration fuel cut is performed, the catalyst temperature itself is lower than that in the case where the deceleration fuel cut is not performed, but the catalyst center portion is reduced. It is shown that the temperature difference between the central part of the catalyst and the peripheral part of the catalyst becomes large because the part where the flow rate of air is large is rapidly cooled. Therefore, it is conceivable to prohibit the deceleration fuel cut when the temperature of the catalyst is high. However, if it is prohibited uniformly, the chances of the fuel cut are reduced and the fuel efficiency is deteriorated.

Therefore, as can be seen from FIG. 8, paying attention to the fact that there is a certain amount of time until the temperature deviation increases,
Under the condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature, the deceleration fuel cut is prohibited when the cumulative displacement or the cumulative period from the start of the deceleration fuel cut exceeds a predetermined threshold. To do. This technical idea is embodied by the deceleration fuel cut control routine of FIG. 5 or 6.

FIG. 5 is a flow chart of the deceleration fuel cut control routine in the first embodiment. This routine is executed every predetermined time. In S31, it is determined whether or not the deceleration F / C flag = 1 indicating that the deceleration fuel cut is being executed.
If the deceleration F / C flag = 0, the process proceeds to S32. S32
Then, it is determined whether or not the prohibition flag = 1 indicating that the deceleration fuel cut is prohibited, and when the prohibition flag = 0,
Proceed to S33.

In S33, it is determined whether or not the normal deceleration fuel cut condition (deceleration F / C condition). Specifically, when the vehicle is in a decelerating state and the engine speed is equal to or higher than a predetermined speed, the deceleration F / C condition is set. In this case, when the idle switch is ON (throttle valve is fully closed), the engine speed is The deceleration F / C condition is that the number Ne is equal to or higher than a predetermined fuel cut rotation speed Nfc (further, the vehicle speed VSP is equal to or higher than a predetermined value).

When the deceleration F / C condition is not satisfied, this routine is terminated, but when the deceleration F / C condition is satisfied, S3 is executed.
Go to 4. In S34, the catalyst temperature Tc at the start of deceleration fuel cut is measured. Although the catalyst temperature sensor 18 that directly detects the catalyst temperature Tc is used here, it may be indirectly detected from the exhaust temperature on the downstream side or may be estimated from the engine operating state.

In next step S35, it is determined whether or not the measured catalyst temperature Tc is higher than a predetermined temperature. The predetermined temperature here is a temperature that corresponds to after the operation of the rotation limiter or the vehicle speed limiter or after the high load operation, and is set to 900 ° C., for example. If the catalyst temperature Tc at the start of the deceleration fuel cut is lower than the predetermined temperature, there is no risk of damage due to the occurrence of temperature deviation in the catalyst even if the deceleration fuel cut is executed.
To S39, the deceleration F / C flag is set to 1, and this routine is ended. As a result, the deceleration fuel cut is started.

If the catalyst temperature Tc at the start of the deceleration fuel cut is higher than the predetermined temperature, the deceleration fuel cut is executed conditionally, and therefore the routine proceeds from S35 to S36. In S36, the restriction flag is set to 1. Further, in S37, since the calculation of the cumulative exhaust amount from the start of the deceleration fuel cut is started, the cumulative exhaust amount ΣQ = 0 is set. Further, in S38, referring to the table of FIG. 9A, the threshold value ΣQ # for the cumulative exhaust amount is set from the catalyst temperature Tc at the start of deceleration fuel cut. Also,
Here, the threshold value ΣQ # is set with a smaller characteristic as the catalyst temperature Tc is higher. After this, proceed to S39 to decelerate F / C
This flag is set to 1 and this routine is completed. As a result, the deceleration fuel cut is started.

After the deceleration fuel cut is started, the deceleration F / C flag is 1 as determined in S31, so the routine proceeds to S40. S
At 40, it is determined whether the restriction flag = 1. If the restriction flag = 1, that is, if the catalyst temperature Tc at the start of deceleration fuel cut is higher than the predetermined temperature, the process proceeds to S41.

In S41, the cumulative displacement ΣQ is calculated.
Specifically, the detected value of the intake air amount Qa equivalent to the exhaust amount is integrated (ΣQ = ΣQ + Qa). In next S42, it is determined whether or not the cumulative displacement ΣQ exceeds a predetermined threshold ΣQ #. If the cumulative displacement ΣQ exceeds the predetermined threshold ΣQ #, the temperature deviation inside the catalyst gradually increases and there is a risk of damage to the catalyst. Therefore, the process proceeds to S43, where the deceleration fuel cut is prohibited. Flag = 1. And further S
45, the deceleration F / C flag is set to 0, and S4
In step 6, the restriction flag is set to 0, and this routine ends. As a result, the deceleration fuel cut is completed and the fuel injection is restarted.

Further, during the deceleration fuel cut, the determination in S44 is made. In S44, it is determined whether or not the deceleration fuel cut recovery condition is satisfied. Specifically, the recovery condition is that the idle switch is turned off (the accelerator pedal is stepped on) or the engine speed Ne becomes equal to or lower than a predetermined recovery speed Nrc.

If it is not the recover condition, this routine is ended, but if the recover condition is satisfied, the routine proceeds to S45. In S45, the deceleration F / C flag is set to 0, and
In S46, the restriction flag is set to 0, and this routine ends. As a result, the deceleration fuel cut is completed and the fuel injection is restarted.

In the condition that the catalyst temperature at the start of deceleration fuel cut is higher than the predetermined temperature, the cumulative exhaust amount ΣQ after the start of the deceleration fuel cut exceeds the predetermined threshold value and the deceleration fuel cut is prohibited. From the next time onward, since the prohibition flag = 1 in the determination in S32, the process proceeds to S47. In S47, it is determined whether or not a predetermined time has elapsed since the prohibition of deceleration fuel cut, and this routine is ended as it is until the predetermined time elapses. However, when the predetermined time elapses, the process proceeds to S48 and the prohibition flag = 0. After this, this routine is ended.

FIG. 6 is a flow chart of a deceleration fuel cut control routine in the second embodiment. This routine is also executed every predetermined time. Here, under the condition that the catalyst temperature at the start of deceleration fuel cut is higher than the predetermined temperature, the deceleration fuel cut is prohibited when the cumulative period (accumulation time) from the start of the deceleration fuel cut exceeds the predetermined threshold. I am trying to do it. That is, the only difference is that the cumulative period is used instead of the cumulative displacement.

Therefore, S37, S38, S41, S42
Only the part of is different. In S37, since the calculation of the cumulative period from the start of the deceleration fuel cut is started, the cumulative period ΣT =
Set to 0. Further, in S38, the threshold value ΣT # for the cumulative period is set based on the catalyst temperature Tc at the start of deceleration fuel cut with reference to the table of FIG. 9B. Also here
The threshold value ΣT # is set with a smaller characteristic as the catalyst temperature Tc is higher.

In S41, the cumulative period ΣQ is calculated. Specifically, the execution time interval ΔT of this routine is integrated (Σ
T = ΣT + ΔT). Then, in S42, the cumulative period ΣT
Exceeds a predetermined threshold ΣQ #. When the cumulative period ΣT exceeds the predetermined threshold ΣT #, the deceleration fuel cut is prohibited because the temperature deviation inside the catalyst gradually increases and the catalyst may be damaged (S43, S45, S).
46).

FIG. 10 is a time chart of this control.
When shifting from the high temperature state to the deceleration operation, the deceleration fuel cut is performed, but when the cumulative displacement or the cumulative period reaches the threshold value, the deceleration fuel cut is prohibited and the fuel injection is restarted. The portion of S1 → S5 of the routine of FIG. 2 and the routine of FIG. 3 correspond to the rotation limiter means. The S2 → S5 portion of the routine of FIG. 2 and FIG.
This routine corresponds to the vehicle speed limiter means. The S3 → S5 portion of the routine of FIG. 2 and the routine of FIG. 5 or 6 correspond to the deceleration fuel cut means. Further, particularly S32, S34 to S38, S40 of the routine of FIG. 5 or FIG.
The portions from S43 to S45 correspond to the deceleration fuel cut prohibition means.

According to the present embodiment (the first embodiment or the second embodiment), under the condition that the catalyst temperature at the start of the deceleration fuel cut is higher than the predetermined temperature, the cumulative exhaust amount after the deceleration fuel cut is started. Alternatively, by providing deceleration fuel cut prohibition means for prohibiting deceleration fuel cut when the cumulative period exceeds a predetermined threshold value, deceleration fuel cut can be performed as much as possible within a range not causing damage to the catalyst, and fuel consumption is improved. Can be achieved.

Further, according to this embodiment, under the condition that the catalyst temperature at the start of the deceleration fuel cut is lower than the predetermined temperature, the predetermined recovery is performed regardless of the cumulative exhaust amount or the cumulative period after the start of the deceleration fuel cut. By continuing the deceleration fuel cut until the condition is satisfied, it is possible to improve fuel efficiency. Further, according to the present embodiment, the threshold value for the cumulative displacement or the cumulative period is set according to the catalyst temperature at the start of the deceleration fuel cut, and in particular, the smaller the higher the catalyst temperature at the start of the deceleration fuel cut, the smaller the threshold value. By setting the characteristics, it is possible to achieve both high levels of prevention of catalyst damage and improvement of fuel efficiency by appropriate setting.

Further, according to the present embodiment, when the catalytic converter is arranged directly below the exhaust manifold, when the catalytic converter is configured to include a ceramic carrier, and the ceramic carrier has a thin wall thickness of 3 mils or less. When applied to a wall carrier, a greater effect of preventing catalyst damage can be obtained under conditions where catalyst damage is likely to occur. Furthermore,
According to the present embodiment, the condition that the catalyst temperature at the start of the deceleration fuel cut is higher than the predetermined temperature is the deceleration fuel cut after the operation of the rotation limiter means or the vehicle speed limiter means, and thus the rotation limiter or the vehicle speed limiter After the operation, it is possible to prevent the catalyst from being damaged by reliably responding to the rise of the catalyst temperature that cannot occur during the normal operation.

[Brief description of drawings]

FIG. 1 is a system diagram of an engine showing an embodiment of the present invention.

FIG. 2 is a flowchart of a fuel injection control routine.

FIG. 3 is a flowchart of a rotation limiter control routine.

FIG. 4 is a flowchart of a vehicle speed limiter control routine.

FIG. 5 is a flowchart of a deceleration fuel cut control routine in the first embodiment.

FIG. 6 is a flowchart of a deceleration fuel cut control routine in the second embodiment.

FIG. 7 is a diagram showing changes in catalyst temperature during deceleration during normal operation.

FIG. 8 is a diagram showing a change in catalyst temperature during deceleration from a high temperature state.

FIG. 9 is a diagram showing a threshold setting table.

FIG. 10 is a time chart of this control

[Explanation of symbols]

1 engine 4 Throttle valve 5 intake manifold 6 Fuel injection valve 8 exhaust manifold 11 Catalytic converter 12 ECU 13 Crank angle sensor 15 Throttle sensor (idle switch) 18 Catalyst temperature sensor 19 vehicle speed sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 312 F02D 45/00 312Z 314 314Z F term (reference) 3G084 BA09 BA13 CA06 DA02 DA35 EA11 EB12 FA05 FA07 FA10 FA20 FA27 FA29 FA33 FA38 3G091 AA02 AA11 AA17 AA23 AA28 AB01 BA08 BA10 CA13 CB02 DA01 DA02 DA03 DA08 DA10 DB06 DB10 DC01 EA01 EA05 EA07 EA16 EA18 EA30 EA31 HA36 GB03 GB31 GB10X3 GB13 GA03 GB13 FB11 GA10X3 DA01 DA04 DA05 DA06 DA07 DA09 DA11 DB05 EA04 FA07 FA11 3G301 JA02 JA34 KA16 KA26 KA27 MA01 MA11 MA24 MA25 NA08 NB11 ND02 PA01Z PA11Z PD03Z PD12Z PE01Z PE03Z PE08Z PF01Z

Claims (13)

[Claims] 1. An exhaust passage provided with a catalytic converter,
In an internal combustion engine equipped with a deceleration fuel cut means that cuts fuel during deceleration operation, the accumulated exhaust amount after starting deceleration fuel cut is a predetermined threshold value under the condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature. A control device for an internal combustion engine, comprising: deceleration fuel cut prohibition means for prohibiting deceleration fuel cut when the speed exceeds. 2. Under a condition that the catalyst temperature at the start of deceleration fuel cut is lower than a predetermined temperature, the deceleration fuel cut is performed until a predetermined recovery condition is satisfied, regardless of the cumulative exhaust amount after the start of the deceleration fuel cut. The control device for an internal combustion engine according to claim 1, which is continued. 3. The control device for an internal combustion engine according to claim 1, wherein the threshold value for the cumulative displacement is set according to the catalyst temperature at the start of deceleration fuel cut. 4. The control device for an internal combustion engine according to claim 3, wherein the threshold value for the cumulative displacement is set with a smaller characteristic as the catalyst temperature at the start of deceleration fuel cut is higher. 5. An exhaust passage provided with a catalytic converter,
In an internal combustion engine equipped with a deceleration fuel cut means that cuts fuel during deceleration operation, the accumulation period from the start of deceleration fuel cut has a predetermined threshold value under the condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature. A control device for an internal combustion engine, comprising deceleration fuel cut prohibition means for prohibiting deceleration fuel cut when exceeding. 6. When the catalyst temperature at the start of deceleration fuel cut is lower than a predetermined temperature, the deceleration fuel cut is continued until a predetermined recovery condition is satisfied regardless of the cumulative period from the start of the deceleration fuel cut. The control device for an internal combustion engine according to claim 5, wherein: 7. The control device for an internal combustion engine according to claim 5, wherein the threshold value for the cumulative period is set according to the catalyst temperature at the start of deceleration fuel cut. 8. The control device for an internal combustion engine according to claim 7, wherein the threshold value for the cumulative period is set to have a smaller characteristic as the catalyst temperature at the start of deceleration fuel cut is higher. 9. The method according to claim 1, wherein the catalytic converter is arranged immediately below the exhaust manifold.
13. A control device for an internal combustion engine according to any one of 1. 10. The catalytic converter according to claim 1, wherein the catalytic converter includes a ceramic carrier.
13. A control device for an internal combustion engine according to any one of 1. 11. The control device for an internal combustion engine according to claim 10, wherein the ceramic carrier is a thin-walled carrier having a wall thickness of 3 mils (= 0.076 mm) or less. 12. The condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature is that the deceleration fuel cut is performed after the operation of the rotation limiter means that cuts the fuel when the engine speed exceeds the allowable speed. The control device for an internal combustion engine according to any one of claims 1 to 11, characterized in that. 13. The condition that the catalyst temperature at the start of deceleration fuel cut is higher than a predetermined temperature is that the deceleration fuel cut after the operation of a vehicle speed limiter means for performing fuel cut when the vehicle speed exceeds an allowable vehicle speed. The control device for an internal combustion engine according to any one of claims 1 to 11.